On 11/12/11 10:22 AM, Allen Wirfs-Brock wrote:
Note that the only specialness of Array instances relates to what happens when you add
new array elements or dynamically change the value of the "length" property.
1) In ES5 this is just not true; there are various parts of the spec
that check [[Class]]. Yes, I know we're working on getting rid of them,
but we haven't gotten to that future world yet.
2) In implementations the above may or may not be true.
So, if you want the objects to be an immutable, array-like object that inherits
from array.prototype through an intermediate prototype there really is no
problem. A JS programmer could express this today in ES5:
var DOMFindResultProto = Object.create(Array.prototype); //make it inherit
from Object.prototype
DOMFondResultProto.someMethod = function O() { ...};
//other prototype methods
//...
function FindResultFactory(nodes) {
var obj = Object.create(DOMFindResultProto);
for (var i=0; i<nodes.length;++i) obj[i]=nodes[i];
return Object.freeze(obj);
}
The result will not have the same performance characteristics as an
actual array in many of today's JITs, for what it's worth. You can
consider this a bug in those JITs, of course.
-Boris
